Vaccines have proven to be the most effective agents for the control of infectious diseases. Control is accomplished by limiting the replication of pathogens through the induction of antigen specific immune responses. Specific cytotoxic T lymphocyte (CTL) responses are integral to the control of a number of viral infections. A growing number of investigators believe that an efficacious vaccine against HIV-1 will need to induce a CTL response. Furthermore, the generation of strong and broad cellular and humoral responses appear to correlate with the maintenance of the asymptomatic state in long-term non-progressors. Recently, DNA-based vaccines have received attention for the development of vaccines against HIV-1. We have demonstrated the induction of humoral and cellular responses by DNA vaccines in a number of animal models including the chimpanzee model. We recently reported on the protection of chimpanzees from infection with HIV-1 by immunization with DNA vaccines. Although this result is encouraging, the infection with HIV-1 by immunization with DNA vaccines. Although this result is encouraging, the immune responses induced by DNA vaccines against HIV-1 need to be further characterized and optimized. The flexibility of molecular biology affords us a number of avenues to pursue in optimizing these induced immune responses. In addition, immunologic advances provide several techniques to aid in characterizing important details about the mechanism of DNA vaccine- induced immune responses and correlating the responses with protection. This proposal outlines a five year plan designed to examine the immune responses induced by DNA vaccines against HIV-1 in both animal models as well as human subjects. The program proposed by the five principle investigators will focus on the generation of improved DNA immunogens through engineering gene expression cassettes which will co-deliver cytokines as well as other immunostimulatory gene sequences. This program will test the ability of such second generation vaccines to impact on HIV replication in animals, models and to modulate HIV immune responses. The goal of the cellular immunology core is to determine the magnitude and character of cellular responses induced in chimpanzee and human subjects. This core facility will collaborate with Projects 1 and 2 to aid in the investigation of the cellular responses induced in the macaque studies. More specifically, the cellular immunology core will delineate CTL and lymphocyte proliferative responses, and the immune activation following immunization with second generation DNA vaccines including testing for cross-clade CTL activity. This core will also attempt to profile the activation of the different cellular populations as well as the cytokine profiles induced following DNA plasmid vaccination. It is likely that this will aid in the development for world wide distribution.